Die for molding of a cuff on a plastic tube

Abstract

 A die (1) for molding a cuff on a plastic tube, comprising an upper shell (2) and a lower shell (3) defining a molding cavity (4) between them; each of said shells (2, 3) has an external structure (6) and an internal wall (7) for defining a half of the molding cavity (4) and for defining a hollow space (8) with the external structure (6). The molding cavity (4) and hollow spaces (8) are separated from each other by internal walls (7). The die comprises openings (9, 10) which are connected with the molding cavity (4) and the hollow spaces (8) respectively

Description

[0001] The present invention concerns a die for molding a cuff on a plastic tube.

[0002] In particular the die object of the present invention is advantageously, but not exclusively, used for molding a cuff on a tracheal tubes or a tracheostomy cannula.

[0003] Here and hereinafter the term "cuff" is intended to mean an inflatable balloon attached around a tube, e.g. a tracheal tube. In tracheal tubes the purpose of the cuff is to function as a seal between tube and trachea, in order to prevent air from getting out and bacteria to enter the lungs. In other catheters, e.g. urine catheters, the purpose of the cuff is to block and secure the tube in the body part where it is inserted into.

[0004] Tracheal tubes are used as means of conveying air or gas mixtures delivered by an Intensive Care Unit or Anaesthesia ventilator, through a breathing circuit, into the patient airways. Tracheostomy cannulas can have the same use as tracheal tubes or can be installed on spontaneously breathing patients who for a particular disease or accidental reasons cannot breath autonomously and sufficiently without this airway bypass.

[0005] Usually, the cuff is obtained through a blowing process or an alternative technology of pre-extruded tubing expansion. The assembly process of the cuff on the tube consists of the following phases:

• cutting of the cuff ends, named collars;
• insertion of the so obtained cuff on the tube and correcting its positioning;
• gluing with solvents or adhesive.

[0006] The result obtained from the above process is the formation of a kind of step next to the collar cutting edge. This step represents a traumatic factor during intubation operation because of the possible abrasions it can cause. This problem is particularly relevant for children and infant patients where the diameter of the tubes is narrower and the collar thickness is crucial.

[0007] Another problem of the prior art process relates to a manufacturing issue. In fact, the shaping and the assembly operations render the whole process slow, expensive and relying heavily on personnel experience and ability. It is important to notice that such problems become more relevant when the tube has a narrow diameter (e.g. for children and infant patients) and when the cuffs are made of polyurethane (PU) with reduced thickness and easy to damaged during handling, tubing and gluing.

[0008] Another way to obtain a cuff on tubes is disclosed on EP1733752. This method provides the production of silicon catheters comprising the adding of a antibonding agent in the zone of the cuff shaping. As it can be easily understood, the adding of a antibonding agent could entail time wasting and high cost problems.

[0009] The aim of the present invention is to achieve a die for molding cuffs on plastic tubes whose technical characteristics are such to obtain said molding in a simple and effective way.

[0010] The object of the present invention is to achieve a die for molding cuffs on plastic tubes whose essential characteristics are reported in claim 1 and 8, and whose preferred and/or auxiliaries characteristics are reported in claims 2 to 7 and 9 to 19.

[0011] For a better understanding of the present invention, a preferred embodiment is described, in an illustrative and not limitative way, with a reference to the accompany drawings in which

figures 1-6 show the die of the present invention during six different manufacturing steps;

figures 7a-7g show the manufacture of a tube for use with the die of the present invention and

figures 8a-8b show an alternative method of manufacture of the tube for use with the die of the present invention.

[0012] Figure 1 shows a die of the present invention as a whole, with the reference number 1.

[0013] The die 1 comprises an upper shell 2 and a lower shell 3, which can be coupled in order to form a molding cavity 4, wherein a portion of a tube 5 is fluid-tightly housed in order to manufacture the cuff.

[0014] Each shell 2 and 3 comprises an external box structure 6 and an inner wall 7, having a semi-ovoid shape and closing the external box structure 6. The internal wall 7 delimits the half of the molding cavity 4. Between the external box structure 6 and the internal wall 7 is then defined a hollow space 8. In the external box structure it is formed a first plurality of canalizations 9 connecting the molding cavity 4 to the outside, and a second plurality of canalizations 10 connecting the hollow space 8 to the outside.

[0015] Referring now to figures 2-6, it is described hereinafter the use of the die of the present invention.

[0016] As shown in figure 2, a hot liquid is injected through canalizations 9 into the molding cavity 4, which houses the portion of tube 5 to be molded. The hot liquid comes therefore in contact with a portion of the sheath of the tube 5 for softening it in order to be able to model it. In particular, the sheath 5a does not adhere to the underlying tube because of the air between the contact surfaces, as will be described subsequently.

[0017] Once a pre-determined period of time, sufficient for the softening the sheath 5a, has elapsed, the hot liquid is extracted through the same canalizations 9 (figure 3) by means of a light vacuum. During the extraction of the hot liquid, the portion of softened sheath 5a is suctioned towards the internal wall 7, shaping itself on it.

[0018] Now, a cold liquid is inserted into the hollow space 8 through canalizations 10 (figure 4). The cooling due to the cold liquid on the internal wall 7 stiffens the portion of sheath 5a, thus letting it take its final shape.

[0019] Once the portion of sheath 5a has taken its final shape, the cold liquid is extracted through canalizations 10 (figure 5), and the die is opened (figure 6) for extracting the tube 5 whereon the cuff 11 is formed.

[0020] For providing a more complete understanding of the present invention, the manufacture of a tracheal tube for use with the die of the present invention will now be described.

[0021] In figure 7a a tracheal tube, extruded and successively cut at the desired length, is indicated with 21. A superficial incision 22 has been cut out on the tracheal tube 21 to connect an inflation lumen (already known and not illustrated for the sake of simplicity) to the outside in relation to the cuff to be provided as described hereinafter.

[0022] Figure 7b shows a metal core 23 around which the tracheal tube 21 is placed to form an assembly 24. In particular, the metal core 23 is hollow and comprises a connecting end 23a to be connected to a feeding line for compressed air L, and a truncated conical end 23b having some holes (not shown) for the outlet of the compressed air. As shown, the second end 23b having a truncated conical shape remains outside the tracheal tube 21.

[0023] Figure 7c shows a second assembly 25 comprising an extruded and cooled sheath 26 inserted inside a metal tube 27. The position of the sheath 26 in the tube 27 is kept fixed by means of a clamp 28. In particular, the metal tube 27 has an inner diameter larger than the diameter of the sheath 26, so that said sheath 26, once inflated, can take on the size of the metal tube 27.

[0024] As shown in figure 7d, the assembly 25 is connected to the assembly 24 by bringing the truncated conical end 23b inside a first end of the sheath 26. The air injection through the truncated conical end 23b starts in this position, while at the same time the assembly 24 slides inside the assembly 25 obtaining a new assembly 29. During the sliding of the assembly 24 inside the assembly 25 the outcoming air inflates the sheath 26 and keeps it adherent to the metal tube 27 by simultaneously forming an air cushion around the tracheal tube 21. The thus formed air cushion allows the tracheal tube 21 to slide into the sheath 26, which, having an inner diameter smaller than the outer diameter of the tube and being made of an elastic material, stays adherent to the tracheal tube 21 as soon as the air cushion collapses.

[0025] Figure 7e shows the splitting up of the assembly 29 once the sheath 26 has completely adhered to the tracheal tube 21. The splitting up occurs by releasing the clamp 28 and extracting from the metal tube 27 the tracheal tube 21 and the sheath 26 surrounding it. Once extracted, the portion of sheath 26 is cut in relation to the truncated conical end 23b, while inside the metal tube 27 a new portion of sheath 26 is placed for a new production cycle.

[0026] Figure 7f shows the detachment of the metal core 23 from the tracheal tube 21, while the sheath 26 undergoes a finishing cut for adapting it to the size of the tracheal tube 21, thus obtaining the semifinished product of medical tube 30.

[0027] Figure 7g shows the semifinished product 30 whereon an incision 31 is cut out for connecting in use the inflation lumen with a portion of the inflation tube it will be glued onto. The semifinished product 30 is suitable for insertion into the die 1 of the present invention.

[0028] With a reference to figures 8a-8b, a second method for the manufacture of a tracheal tube is shown, which differs from the one relating to figures 7a-7g because of its larger automation.

[0029] Figure 8a shows a continuously extruded tracheal tube 41, cooled with air and on which a superficial incision 42 is cut out at a predefined distance for connecting the inflation lumen (already known and not shown for the sake of simplicity) to the cuff to be provided as described hereinafter. The tracheal tube 41 has such a stiffness that it does not need a metal core as was needed in the embodiments of figure 7.

[0030] Figure 8b shows a covering step of the tracheal tube 41 with a sheath 43. Once cooled and incised as previously described, the tracheal tube 41 is continuously inserted in a second extrusion head 44 by means of which the covering sheath 43 is produced by overextrusion. In particular, plastic material enters the extrusion head 44 through an inlet 44b and is overextruded around tube 41 forming the said sheath 43. During the overextrusion of the sheath 43, some air is injected at regular intervals between the tracheal tube 41 and the forming sheath 43. In particular, the air enters the extrusion head 44 through an inlet 44a, in use connected to a feeding line of compressed air, and is injected in relation to the superficial incisions 42 between the sheath 43 and the tracheal tube 41 so that some non-adhesion areas are formed around said incisions 42. It is thus obtained a semifinished medical tube 45 comprising a regularly distributed plurality of swellings 46 of the sheath 43 in the areas around the incisions 42. Afterwards, regularly distributed incisions 47 are cut out for connecting in use the inflation lumen to respective portions of the inflation tube they will be glued onto.

[0031] As shown by the aforesaid description, the die of the present invention is particularly simple, both in its manufacture and in its use.

[0032] In addition, the die of the present invention can be advantageously used in plastic tubes which have been covered with a sheath having antimicrobial activity.

Claims

1. Die (1) for molding a cuff on a plastic tube, the die comprising an upper shell (2) and a lower shell (3) defining a molding cavity (4) between the upper and lower shells for the insertion therein of said plastic tube; said die (1) being characterized in that each of said shells (2, 3) has an external wall structure (6) and an internal wall (7), the wall of a respective shell defining a half of said molding cavity (4) and the wall structure and the wall of each shell defining a hollow space (8) there between; said molding cavity (4) and said hollow spaces (8) being separated from each other by said internal walls (7); said die comprising openings (9, 10) which are connected with said molding cavity (4) and said hollow spaces (8) respectively.

2. Die (1) according to Claim 1, characterized in that said molding cavity (4) and said hollow spaces (8) are able to be occupied by a fluid which is inserted and extracted through said openings (9, 10).

3. Die (1) according to Claim 2, characterized in that said fluid is a liquid.

4. Die (1) according to anyone of the preceding Claims, characterized in that said external structure has a box shape (6).

5. Die (1) according to anyone of the preceding Claims, characterized in that the internal wall (7) has a semi-ovoid shape.

6. Die (1) according to anyone of the preceding Claims, characterized in that said plastic tube is a medical tube.

7. Die (1) according to Claim 6, characterized in that said medical tube is a tracheal tube or a tracheostomy cannula.

8. Molding process for manufacturing a cuff on a plastic tube by means of a die according to any one of the preceding Claims; said process being characterized in that it comprises:

- an insertion step, wherein a tube (5) is tightly housed in a molding cavity (4);

- a softening step, wherein a portion of the sheath (5a) of the tube (5) is softened by using a fluid;

- a molding step, wherein the portion of softened sheath (5a) adheres to internal walls (7); and

- a stiffening step, wherein the portion of sheath (5a) adhering to the internal walls (7) is stiffened by using another fluid.

9. Molding process according to Claim 8, characterized in that in said softening step a fluid is injected in said molding cavity (4) contacting and softening the sheath (5a).

10. Molding process according to Claim 9, characterized in that said fluid is a hot liquid.

11. Molding process according to Claim 10, characterized in that in said stiffening step another fluid in injected into a hollow space (8) of the die (1) stiffening the sheath adhering to the internal walls (3).

12. Molding process according to Claim 11, characterized in that said another fluid is a cold liquid.

13. Molding process according to any one of the Claims from 7 to 11, characterized in that said molding step is carried out by suctioning out the fluid used in said softening step.

14. Molding process according to Claim 13, characterized in that in said molding step the fluid is suctioned out through openings (9) by means of a light vacuum.

Drawing